<!DOCTYPE html>
<html>

	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>

	<body>
		<span>
			信就是所望之事的实底，是未见之事的确据。
		</span>
	</body>

</html>

<style type="text/css">
	/*使用inline-flex布局时字体水平和垂直居中*/
	span {
		/*设置为inline-flex*/
		display: inline-flex;
		border: 1px solid green;
		height: 100px;
		width: 600px;
		/*水平居中*/
		justify-content: center;
		align-items: center;
	}
</style>